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**whacker** · 08-08-2006, 07:51 PM

Worn out distributor? Or maybe the distributor clamp is loose? You might also check your spark plug wires, and pull your spark plugs to read the tips. They should all be consistant, a kind of dull brown with little or no carbon residue. I bet you will find one that looks different from the rest, and that will be the bad cylinder. Could be a cracked plug insulator or a bad wire to that plug. A miss at speed is usually electrical.

**StudeRich** · 08-08-2006, 10:26 PM

It sounds like your Lark is starving for fuel, have you looked at the flex hose at the pump and tank for a loose or cracked one, and check all of the line for a crushed portion, or even a forgotten fuel filter somewhere in the line that has been added and is clogged!
Rich.

quote:[i]
60 Lark 259. The problem is that the engine misses when driving at a consistant speed over 50mph. It started slowly as just a little miss here and there. Now it just loses all power as if I`m running out of gas. It starts and runs excellent until I take it out on the highway and then the trouble starts. I try to feather the throttle, clutch it and rev it a little but nothing works. If I just put the clutch in the motor stalls. I will coast to a near stop , pop the clutch and the motor fires back up and will behave as long as I drive it under 50mph.
I have replaced the fuel pump, coil, resistor, rebuilt the carb. The points appear to be fine. I have checked the heat riser valve in the exhaust manifold and it seems to function easily. Anybody?

StudeRich
Studebakers Northwest
Ferndale, WA

**Roscomacaw** · 08-09-2006, 07:37 AM

Or a gas cap that's not venting properly? By the time you coast to a stop, the slightly venting cap has finally let enough air in to lessen the vacuum so the pump can pull again.
Higher speeds, require higher fuel flow - higher fuel flow elevates the vacuum condition in a tank that can't draw ambient air in to relieve the vacuum created by the constant call of the fuel pump, hence misfiring for starvation.

I've meant to say - harkening back to an earlier thread - that the BS about have a cap that holds good pressure to ensure adequate fuel flow is just plain wrong. There's no Stude vehicle that depends upon fuel tank pressure build-up for proper performance. Not unless it's maybe had some sort of BrandX FI engine installed.[8D]

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS

**Yesca** · 08-09-2006, 08:13 AM

I have not checked the lines from the tank to the pump. I will do that this morning. The cap is most likely the stock cap. would it ....go bad? I will also pull the plugs and take a peek.

The first time it stumbled I immediately thought "out of gas". And that`s still what it feels like. no popping, backfiring,and if it were ignition how would it run so well when not on the highway? It fires right up and takes off like a bat out of hell.

**PackardV8** · 08-09-2006, 08:13 AM

While your symptoms suggest a fuel feed restriction, need more info to help with the diagnosis:

1. If you don't have a inside-mounted tach, run temporary wires so you can hook up some kind of temporary tach. Even a tune-up dwell tach will do.

2. On a safe, open stretch of road, from idle, put the accelerator to the floor and accelerate to max rpms in the lower gears. What rpm does your miss start? Is it the same rpm in each gear? Is it load dependent or rpm dependent? Load dependent miss most likely ignition. RPM dependent can be either.

3. When in doubt, replace all ignition components - plugs, wires, cap, rotor, points, condensor and resistor. They are inexpensive and then you know where you are.

4. Do you have a Prestolite distributor? They are infamous for wearing out the advance weight bushings.

5. Temporarily install a fuel pressure gauge. Put the rear of the car on jack stands. Accelerate to the rpm where the miss occurred on the road and then load the engine using the brakes. Have someone watching the fuel pressure gauge. If it is 4-7 psi at idle and then drops to zero before the miss begins, you have your problem defined. Let the brakes cool for five minutes between tests.

thnx, jv.

PackardV8

**Guest** · 08-09-2006, 08:16 AM

Try a brand new gas cap. I had a similar problem with my 49 Commander. Stant makes brand new caps that will fit the Lark.
[8D]

Restore it, don't replace it.Keep the Studebaker reproduction industry going

**Yesca** · 08-09-2006, 09:23 AM

I think I got a little ahead of myself. Before rebuilding the carb, if I let the car sit more than a day without starting it, it would not fire up without being primed first. I assumed it was my carb leaking. So, along with the accelerator pump plunger being dust,I thought the rebuild would remedy the problem. Well, it hasn`t. I just killed my battery attempting to start it.

Are these two problems (Losing all power at high speed/not having fuel to start after 2 days of sitting) related? this car did sit for a few years.....and I dread to know what the inside if the fuel tank looks like....

**PackardV8** · 08-09-2006, 02:11 PM

Probably. If you have some sort of trash restriction in the fuel system: tank, lines, pump, filter, carb, the two problems you mention could result.

First, When you were trying to start it, did you get two strong squirts out of your accelerator pump every push? If not, disconnect the line into the pump, attach a piece of clean hose and blow back through it. Use mouth pressure only, no 125psi line pressure. Does it blow easily? Can bubbles be heard by listening at the fuel filler neck?

Reconnect the line into the fuel pump and disconnect the line at the carb. Disconnect the hot wire to the coil so there are no sparks. Insert the fuel line into a 3# coffee can and crank over the engine and make sure there is a steady flow of fuel at cranking speeds.

Connect in a fuel pressure gauge and reconnect to the carb. Does the pressure rise to 4-7psi and hold when cranking over?

Do you have a fuel filter and has it been changed?

PackardV8

**Yesca** · 08-09-2006, 02:38 PM

It`s definetly fuel related. My gas cap is working fine. I drove all around city streets without incident. Then I decided to drive it pretty hard in first and there it was. After about 25-30 seconds winding out in first it started to choke out and die. I figure it takes about that long to use all the fuel in the bowl and it can`t replenish the fuel fast enough?! I`m going for a T connector for my vaccum gauge and test my fuel pressure.

I just put in a new fuel pump, filter, and rebuilt the carb. there are no other in line filters and all hoses are in good condition. If I don`t remedy the problem today, I will attempt the blow back method you described to determine if there is blockage in the line or tank.

Thanks!

**Rosstude** · 08-09-2006, 03:44 PM

**Roscomacaw** · 08-09-2006, 04:04 PM

And you checked the fuel cap - how? Not that I insist on being right - just want to eliminate that possibility.
Loosen your gas cap and repeat your demanding driving. With a 60 Lark, you likely won't spill any gas unless you're climbing a hlll with a full tank.

Yes, it could be crap in the lines or in the tank. I once found a shop rag in a gas tank! Maybe someone had used it as a temporary gas cap or put it in as a prank. Either way, it was an effective block of the fuel pickup. There's no filter sock on the pickup tubes, so it's easy for them to get clogged.[}

]

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS

**bams50** · 08-09-2006, 05:30 PM

I'll bet a beer it's fuel starved!

It's probably junk in the tank and/or pickup. First thing I did with my wagon, being a log-time barn stored car, was to disconnect the fuel line from the carb and unplug the electric pump (started it by filling the float bowl thru the vent tube)... second job was pulling the tank; and it had about 5 gallons of varnish, and at least 2 GALLONS of rust and sediment in the bottom!

Years ago my father had a customer bring in his 67 Chrysler with the same symptoms... turned out to be a grasshopper lodged in the pickup tube! [^]

Robert K. Andrews Owner- IoMT (Island of Misfit Toys!)
Parish, central NY 13131

http://www.cardomain.com/ride/2358680/1

**gordr** · 08-09-2006, 07:00 PM

quote:Originally posted by bams50

I'll bet a beer it's fuel starved!

It's probably junk in the tank and/or pickup. First thing I did with my wagon, being a log-time barn stored car, was to disconnect the fuel line from the carb and unplug the electric pump (started it by filling the float bowl thru the vent tube)... second job was pulling the tank; and it had about 5 gallons of varnish, and at least 2 GALLONS of rust and sediment in the bottom!

Years ago my father had a customer bring in his 67 Chrysler with the same symptoms... turned out to be a grasshopper lodged in the pickup tube! [^]

Robert K. Andrews Owner- IoMT (Island of Misfit Toys!)
Parish, central NY 13131

http://www.cardomain.com/ride/2358680/1

Let's not forget that possibly the steel line has some pinhole leaks due to rust, that allow the fuel pump to suck air instead of fuel. That can manifest itself as high-speed starvation.

Also, a bad fuel pump itself can do this, or maybe (remotely possible) a worn fuel pump drive cam.

Also, check the carb, and make sure there's no trash in the fuel inlet fitting, and that the FLOAT DROP measurement meets spec. If the flaot cannot drop far enough, the inlet needle can restrict fuel flow in high-demand situations.

In any case, your problem is clearly due to the fuel supply not meeting the demand of the engine at speed. Find the cause of the weak fule feed, and you should have it licked. Leave the ignition be for now.

Gord Richmond, within Weasel range of the Alberta Badlands

**bams50** · 08-10-2006, 01:36 AM

I meant to add this:

I've seen rubber hoses crack and not show leaks, but suck air on heavy demand! I had a Dodge van years ago that would stumble and sputter just after right hand turns only... turned out to be the short rubber line from the metal line to the fuel pump was dry-rotted, and a crack was opening when the drag link touched it - on right turns only!

That one was sure fun to diagnose.....[}

]

Robert K. Andrews Owner- IoMT (Island of Misfit Toys!)
Parish, central NY 13131

http://www.cardomain.com/ride/2358680/1

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60 lark engine misfire

60 lark engine misfire

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